This project seeks to define the spectrum of liver disease found in Australia Antigen positive blood donors. In particular it concentrates on those donors found to have no clinical or biochemical evidence of liver disease. Intensive case finding and long-term prospective follow up will be used to define the liver disease potential of Australia antigen positivity in such patients. Patients will be identified by screening all blood donated at the Belle Bonfils Memorial Blood Bank for Australia antigen. Positive donors will have clinical examination, biochemical tests, and where applicable, liver biopsy. Biopsies will be studied by light and electron microscopy. These studies should result in a closer definition of the etiologic role of Australia Antigen in the development of chronic liver disease.